Self-cleaning valve for refrigerating apparatus

ABSTRACT

A refrigerating apparatus having a self cleaning valve for use with a liquid refrigerant such as carbon dioxide which exists when the pressure is released only briefly as a liquid and primarily both as a solid and a gas. The valve is self-cleaning in that opening and closing the valve dislodges solid carbon dioxide from the interior which would normally clog a valve with a liquid refrigerant of this type and with the self-cleaning feature comprising a knife edged scraping portion on either the valve seat part or the movable part so as to dislodge deposited carbon dioxide or similar refrigerant solid when the valve is operated. The disclosure also includes an apparatus including means for introducing the fluid refrigerant through a plurality of flow paths that span substantially the full width of a refrigerant chamber and with a self-cleaning valve of the above type positioned in each flow path and primarily exteriorly of the chamber.

[451 Nov. 19, 1974 SELF-CLEANING VALVE FOR REFRHGERATING APPARATUS [75]Inventor: Ronald A. Banike, Elmhurst, Ill.

[73] Assignee: llollymatic Corporation, Park Forest, 111.

[22] Filed: Sept. 29, 1972 [21] Appl. No.: 293,408

[52] US. Cl 137/242, 62/62, 62/384,

137/542, 239/117 [51] Int. Cl. lFl6k 25/00, F25d 3/12 [58] Field ofSearch 62/303; 137/238, 242;

222/148; 239/114, 117, 123, 118; 251/172, 334, DIG. 4, 205, 333; 431/122[56] References Cited UNITED STATES PATENTS 613,623 11/1898 Dolan137/242 1,210,799 l/l9l7 Hawxhurst et al... 137/483 X 1,502,448 7/1924Tanner 251/205 X 1,825,378 9/1931 Wilson 251/333 X 2,738,159 3/1956Fleming 251/333 2,759,336 8/1956 Seefeldt 137/243 X 3,056,575 10/1962Mooney.... 251/172 3,410,521 11/1968 Sowers et al 251/172 X FOREIGNPATENTS OR APPLICATIONS 210,530 2/1924 Great Britain 251/172 PrimaryExaminer-William R. Cline Assistant ExaminerRichard Gerard Attorney,Agent, or Firm-Hofgren, Wegner, Allen, Stellman & McCord 5 7] ABSTRACT Arefrigerating apparatus having a self cleaning valve for use with aliquid refrigerant such as carbon dioxide which exists when the pressureis released only briefly as a liquid and primarily both as a solid and agas. The valve is self-cleaning in that opening and closing the valvedislodges solid carbon dioxide from the interior which would normallyclog a valve with a liquid refrigerant of this type and with theself-cleaning feature comprising a knife edged scraping portion oneither the valve seat part or the movable part so as to dislodgedeposited carbon dioxide or similar refrigerant solid when the valve isoperated. The disclosure also includes an apparatus including means forintroducing the fluid refrigerant through a plurality of flow paths thatspan substantially the full width of a refrigerant chamber and with aself-cleaning valve of the above type positioned in each flow path andprimarily exteriorly of the chamber.

2 Claims, 4 Drawing Figures SELF-CLEANING VALVE FOR REFRIGERATINGAPPARATUS BACKGROUND OF THE INVENTION A refrigerating system of the typeusing a liquid refrigerant that exists principally as a solid or a gaswhen pressure is reduced with a typical refrigerant being liquid carbondioxide is disclosed in the copending application of R. C. Wagner Ser.No. 264,133, filed June 19, 1972 and assigned to the same assignee asthe present application. A typical refrigerant for such a system isliquid carbon dioxide which exists only briefly as a liquid whenpressure is reduced and exists primarily as a mixture of a solid and agas. Valves used to control the flow of the refrigerant in such a systemare subject to complete blockage of flow by the solid refrigerantpacking the inside of the valve. One of the features of this inventionis to provide a refrigerating apparatus including a self-cleaning valvewhere such blockage is prevented.

The most pertinent prior art of which applicant is aware is US. Pat. No.2,759,336 in which there is disclosed a valve for controlling the flowof liquid carbon dioxide and which is self-cleaning in one embodiment bya closing action over large surface areas between a movable part and astationary part. In the present application the self-cleaning featureinstead of utilizing a closing action over a large area functions by ascraping action by providing a scraping portion on one of the valveparts with the result that the self-cleaning is much more reliable andis faster acting.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a shortened horizontalsectional view through an insulated freezing tunnel of a refrigeratingapparatus of the type disclosed in the above copending application andwhich is similar to FIG. 4 of this copending application FIG. 2 is alongitudinal sectional view through a valve embodying the invention.

FIG. 3 is a schematic flow diagram for providing liquid carbon dioxideto three of the valves of FIG. 2 in parallel.

FIG. 4 is an enlarged detail sectional view of the valve of FIG. 2.

DESCRIPTION OF THE PREFERRED EMBODIMENT As disclosed in FIG. 1 and ingreater detail in the above copending application the refrigeratingapparatus which is disclosed for use with liquid carbon dioxide orsimilar refrigerant that exists primarily under reduced pressure as asolid and a gas comprises a tunnel 11 having thermally insulated walls12. The tunnel has an entrance end 13 and an exit end 14 through whicharticles as indicated at 15 are conveyed during refrigeration thereofsuch as for freezing food items. The conveying is accomplished by anendless conveyor belt 16 that is continuously moved in the directionindicated by the arrow 17 from the entrance 13 to the exit 14 duringwhich the articles 15 are frozen, all as described in greater detail inthe above copending application.

The gaseous refrigerant which is formed by the volatilizing of theliquidrefrigerant and the sublimation of the solid refrigerant is recirculatedover the articles by a gas recirculation blower l8 driven by a shaft 19with the recirculated carbon dioxide gas being drawn from beneath thetrailing end 20 of a recirculation baffle 21 and up through a conduitsection 22 as indicated by the arrows 23 and into the entrance 24 to theblower 18.

At the exit 25 from the blower 18 there are provided parallel baffles26, 27 and 28 operating as guide means spaced from each other and havinginner ends 29 spaced from each other to provide a plurality of flowpaths 30, here three, spanning substantially the full width of thetunnel 11 to distribute the refrigerant across this full width.

In order to provide fresh refrigerant to the apparatus 10 the inner endsof the flow paths 30 between the baffles 29 and adjacent the blower 18are provided with a plurality of refrigerant valves 31. As can be seenfrom FIG. 1 each flow path 30 at its entrance which is adjacent theblower 18 is provided with its own valve 31. Also it is possible to usea single valve 31 with a horn of the type shown in the above Wagnerapplication to spread out the flow across the tunnel 11.

With this arrangement the fluid refrigerant which includes flowablevaporizable solid particles and gaseous fluid where the refrigerant iscarbon dioxide or the like is introduced into the apparatus tunnel orchamber 11 at an intermediate section between the entrance l3 and theexit 14. Because of the positioning of the valves 31 the refrigerant isintroduced initially transversely to the chamber 11 and then is turnedthrough 90 by the baffles 26-28 so that at the exits of the flow paths30 the refrigerant is flowing countercurrently to the direction 17 ofmovement of the articles 15 as indicated by the directional arrows 32.Thus the apparatus including the valves as illustrated in FIG. 1produces a manifold effect that spreads the flow of refrigerant in theflow paths 30 across the full width of the tunnel 11 and above the fluidseparating baffle 21.

The flow paths of the refrigerant to the three valves 31 in theillustrated embodiment is shown semischematically in FIG. 3. Here theliquid carbon dioxide is directed through a supply valve 32 and the flowline 33 in parallel to the three valves 31. Flow through these valves 31causes an immediate pressure drop on the liquid carbon dioxide so thatthe exiting refrigerant indicated at 34 is in the form of mixed solidcarbon dioxide and gaseous carbon dioxide formed both from the vaporization of the liquid and the solid. The valves 31 in the illustratedembodiment are located primarily exteriorly of the chamber 11.

The structure of the valve is illustrated in FIGS. 2 and 4. As is shownthere the valve comprises a tubular valve body 35 containing alongitudinally movable valve part 36 therein having on its forward end avalve closing surface 37 in the form of a truncated cone with the smallend joined to the valve stem 38 and the large end adjacent the exit 39of the valve body 35.

Surrounding the surface 37 is an annular valve seat 40 that has asealing surface 41 that engages the closing surface 37 when the valvepart 36 is in closed position as shown in FIG. 2. One of the surfaces 37and 41 is provided with a scraping portion engaging the other surface sothat when the movable part 36 is moved in opening and closing the valvesolid refrigerant deposited within the valve will be scraped by thescraping portion from the other surface. In the illustrated embodimentthe scraping portion is in the form of a knife edge 42 on the seat part40 to engage the closing surface 37 of the movable part 36. The resultis that when the valve part 36 is moved from its closed position asshown in FIG. 2 to its open position or to the right in FIG. 2 thescraping portion 42 scraps deposited solid carbon dioxide therefrom sothat it can be carried from the interior of the tubular body 35 by theflow of refrigerant as indicated by the arrow 43 into and through thevalve.

The scraping portion on the seat part 40 extends around the movablevalve part surface 37 in that it has an annular shape to engage theentire circumference of the surface 37.

The valve is held in closed position as shown in FIG. 2 for movementwithin a bushing 44 by a helical spring 45 that is positioned around thereduced rear end 46 of the stem 38 and has one end bearing against thebushing 44 and the other end bearing against a threaded adjustable nut47.

The movable part 36 of the valve is moved to an open position or to theright in FIG. 2 when liquid carbon dioxide is allowed to flow into thevalve as shown at 43 under a pressure greater than an initial setting onthe valve. That is, the valve is set at some cracking pressure byadjusting the nut 47 to compress the spring 45 to some pre-load which istransmitted to the stem 36. This pre-load is selected so that the valvewill crack open at a pressure above the triple point of carbon dioxide75 PSIA or greater.

Carbon dioxide is stored in a liquid state under a pressure of 305 PSIGand F. and will remain in a liquid state under a pressure range of 60PSIG to 1,051 PSIG and a temperature range of 69.9F. to 87.8F. Toutilize the liquid carbon dioxide as a continuously controlled fluid,that is, to control the flow rate, the valving and controls must containthe carbon dioxide within these boundaries. To accomplish this directivethe shear-orifice valve was developed.

The shear-orifice valve is used in conjunction with a pneumaticallyoperated flow control needle valve as noted in the above Wagnerapplication and here indicated generally at 32 in FIG. 3. As the needlevalve modulates the flow rate, from signals transmitted from an 1/?transducer and controller system, the shearorifice valve modulates. Asthe needle valve modulates the flow rate, the pressure drop across thevalve varies and the shear-orifice valve senses this pressure varianceand modulates.

Although the system is set up to contain the carbon dioxide within itsliquid state boundaries, solid carbon dioxide still forms underconditions of low flow rate and at shut-off. It is also assumed that asthe carbon dioxide exits the nozzle 48 of the shear-orifice valve (areaof high velocity and low pressure), solid particulate flashes backwithin the seat 41 area. The shearorifice valve, with its knife edge,shears what solid matter is formed and self-cleans, keeping the valveopen and free flowing.

This permits the liquid carbon dioxide to flow inwardly of a sideentrance 52 to the valve body 35 and make a right angled turn to flowoutwardly in the annular passage or nozzle 48 that is now formed betweenthe surface 37 and the surface 41. Because this constitutes a rapid dropin pressure at the exit 39 of the valve the released refrigerantindicated at 32 in FIG. 1 and 34 in FIG. 3 becomes a mixed solid andgaseous carbon dioxide refrigerant with a substantially complete absenceof liquid.

When the movable valve part 36 returns to the closed position of FIG. 2solid carbon dioxide tends to be deposited on the interior of the valvebody 35 and particularly in the area around the valve closing surface37. In the ordinary valve this solid carbon dioxide would block theinterior flow passage so that upon subsequent opening of the valve verylittle if any refrigerant would flow therethrough.

In the self-cleaning valve of the present invention because of theprovision of the scraping surface illustrated at 42 the subsequentopening movement of the movable part 36 in the direction indicated bythe arrow 53 would cause the scraping portion or knife edge 42 to scrapethe solid refrigerant from the surface 37 so that the dislodgedparticles of solid refrigerant would be carried out through the exit 39by the refrigerant which is now free to flow through the valve body.

In order that this scraped refrigerant does not itself block the freshflow the seat part 40 of the valve is annularly arranged around thesurface 37 and extends in the opposite direction to the direction ofmovement 53 of the movable part and provides a solid collecting annularpocket 54 between the tapered seat part 40 and the adjacent areas of thevalve body 35. Then when the flow of liquid refrigerant is again startedthis temporarily received solid within the pocket 54 is itself carriedout with the exiting refrigerant 34.

Having described my invention as related to the embodiment shown in theaccompanying drawings, it is my intention that the invention be notlimited by any of the details of description, unless otherwisespecified, but rather be construed broadly within its spirit and scopeas set out in the appended claims.

I claim:

1. A self-cleaning valve for a liquid refrigerant that also exists as asolid, comprising: a valve body having an inlet and an outlet for flowof said refrigerant therethrough in a downstream direction; a valvemovable part in said body mounted for movement along a longitudinal axisand having an annularly tapered substantially rigid valve opening andclosing surface; and an annular valve seat part having a substantiallyrigid seal surface for sealingly engaging said rigid tapered closingsurface, said movable part moving in said downstream direction to openthe valve and modulate refrigerant flow therethrough, said valve seatrigid seal surface comprising a scraping portion for engaging thetapered surface of said movable part, said scraping portion convergingin an upstream direction toward said axis whereby the opening andclosing movements of the movable part result in the scraping portionscraping solid refrigerant from that portion of the movable valvesurface disposed upstream from the area of sealing engagement in thevalve closed position.

2. The valve of claim 1 wherein said scraping portion is annularlycoaxial with and engages said tapered surface only when the valve isclosed.

1. A self-cleaning valve for a liquid refrigerant that also exists as asolid, comprising: a valve body having an inlet and an outlet for flowof said refrigerant therethrough in a downstream direction; a valvemovable part in said body mounted for movement along a longitudinal axisand having an annularly tapered substantially rigid valve opening andclosing surface; and an annular valve seat part having a substantiallyrigid seal surface for sealingly engaging said rigid tapered closingsurface, said movable part moving in said downstream direction to openthe valve and modulate refrigerant flow therethrough, said valve seatrigid seal surface comprising a scraping portion for engaging thetapered surface of said movable part, said scraping portion convergingin an upstream direction toward said axis whereby the opening andclosing movements of the movable part result in the scraping portionscraping solid refrigerant from that portion of the movable valvesurface disposed upstream from the area of sealing engagement in thevalve closed position.
 2. The valve of claim 1 wherein said scrapingportion is annularly coaxial with and engages said tapered surface onlywhen the valve is closed.